Moderate Aerobic Exercise Enhances the Th1/Th2 Ratio in Women with Asthma.

Background: In this study, we aimed to investigate the effects of aerobic exercise training on the serum IL-4/IFN-γ ratio (Th1/Th2 balance), testosterone/cortisol ratio, levels of cortisol, testosterone, estrogen, and progesterone, and body mass index (BMI) and to determine the relationship between changes in these variables in women with asthma. Materials and Methods: Twenty-one women with mild to moderate asthma and regular menstrual cycles were selected in this study. Eleven women in the exercise group participated in the aerobic exercise program (60 min/day, three days a week in the evening). Peripheral blood samples were collected before (week 0) and after (week 12) the program. The samples were analyzed to determine the levels of sex hormones and cortisol via chemiluminescence assay, and cytokines were examined by ELISA assay. Results: The findings showed a significant increase in the Th1/Th2 ratio and a decrease in cortisol and BMI in the exercise group, compared to the control group (P<0.05). There was no significant correlation between changes in cortisol, sex hormones, and BMI and the increase in Th1/Th2 ratio. Conclusion: The present results suggested that moderate aerobic exercise enhances the Th1/Th2 ratio, independent of changes in steroid hormone level and BMI in women with asthma.

higher levels of physical activity were associated with lower levels of systemic inflammation in patients with severe asthma (10). Moreover, De Araujo et al. revealed that regular moderate aerobic training could prevent and reduce lung inflammation by increasing the level of Th1 and decreasing Th2 (11). Also, aerobic exercise has been shown to decrease Th2 response and airway inflammation in a murine model of asthma (12).
Sex is one of the various regulatory factors, which controls the Th1/Th2 balance (13). There is a growing body of research on the role of sex hormones in immune cell and T-cell regulation and development of asthma in women (14,15). Accumulating evidence suggests that sex hormones modify the Th1/Th2 balance by increasing Th2 immune responses in women (15,16). It has been reported that progesterone and estrogen may have synergistic effects on the Th1/Th2 balance and exacerbation of asthma in women. Androgens, on the other hand, shift the Th1/Th2 balance towards a Th1 phenotype (16). According to previous studies, testosterone is likely to restrict immunological and inflammatory processes exacerbating asthma, which may be one of the reasons for the low prevalence of asthma in men, compared to women (17).
Although testosterone is produced in small quantities in the ovaries and adrenal glands, it is an essential hormone for women (18), associated with asthma (19). On the other hand, according to recent findings, cortisol induces a shift in the Th1/Th2 balance towards Th2, compared to testosterone. It inhibits the production of Th1 cytokines and up-regulates the production of Th2 cytokines by immune cells (20,21). The role of glucocorticoids in Th1/Th2 patterns (21), as well as the relationship between psychological stress, cortisol level, and asthma, has been examined in the literature (22).
In addition to sex hormones and cortisol, obesity also affects the Th1/Th2 immune imbalance (23,24) and is considered a risk factor for the development of asthma (25). The association of obesity with the risk of asthma is higher in women than men (26). On the other hand, in obese asthmatic patients, aerobic exercise training may reduce obesity and change the levels of cytokines, which are associated with obesity and asthma. Physical activity also changes the level of female sex hormones (27) and cortisol (28). Therefore, alterations in steroid hormones may be associated with changes in the Th1/Th2 ratio due to exercise.
One of the therapeutic methods for asthma is to restore the Th1/Th2 balance (9). To answer the question of whether changes in obesity and steroid hormones due to exercise training play a role in improving of the Th1/Th2 balance in women, the current study aimed to investigate the effect of 12 weeks of aerobic exercise on changes of Th1 (IFN-γ) and Th2 (IL-4) cytokines, as well as effective factors, including cortisol, testosterone, estrogen, progesterone, testosterone/cortisol ratio, and body mass index (BMI) in asthmatic women.

Subjects
In this clinical trial study, twenty-one inactive women with mild to moderate asthma and regular menstrual cycles (mean age: 35.63±7.4 years; range: 25-42 years) were recruited from Sahand Asthma Clinic in Urmia, Iran. The participants were non-smokers and did not use any hormonal drugs. They also had no major cardiovascular, renal, metabolic, or pulmonary diseases and had a history of regular menstrual cycle over the past three months. Also, they had not participated in regular exercise or diet programs over the past six months. Before the exercise program, a written informed consent was obtained from each participant. All aspects of the study involving human subjects were approved by the local medical ethics committee. Also, all study procedures were in accordance with the principles of the Declaration of Helsinki.
The participants were divided into two groups: exercise (n=11) and control (n=10). The control group received routine medical treatment and did not partake any exercise sessions; their only physical activity involved work or household chores. On the other hand, the exercise group, besides routine medical care, participated in a specific exercise program for 12 weeks (three sessions of aerobic exercise per week in the evening).

Menstrual cycle control
We monitored the menstrual cycle of all participants for at least three months before the intervention. Subjects with irregular menstrual cycles were excluded from the analyses. After recording the length of menstrual cycle, day of ovulation was determined based on the instructions of MAX14 kit (an ovulation predictor kit) and body temperature control. Six to eight days after ovulation (almost day 21 of a 28-day cycle) was considered as the luteal phase. All measurements and blood collections were performed in a constant menstrual phase (mid-luteal phase) in pre-and post-exercise periods.

Training protocol
The exercise program included 12 weeks of aerobic exercise for 60 minutes, three sessions a week, with an intensity of 60-80% of maximum heart rate (MHR). Each

Statistical analysis
Distribution of data in the exercise and control groups was evaluated using the Jarque-Bera test. Baseline characteristics were compared between the control and exercise groups, using unpaired t-test. Also, differences between the exercise and control groups were compared by ANCOVA test, with the baseline value used as a covariate. Pearson's correlation coefficient test and stepwise multiple linear regression were used to determine the relationship between changes in the Th1/Th2 ratio, steroid hormones, and BMI in the exercise group. SPSS version 23 was used for all statistical analyses. Data are shown as mean±SD. P-value less than 0.05 was considered significant.

Subjects
The mean age of subjects with a history of asthma (mean duration: 9.5±3.9 years) was 35.6±7.4 years. There was no significant difference between the groups in terms of age, asthma duration, BMI, or serum concentration of hormones before the exercise program (P>0.05). testosterone/cortisol ratio did not significantly change in the exercise group (P>0.05) ( Table 1).

DISCUSSION
Today, more attention is being paid to the regulation of Th1/Th2 balance in asthmatic patients (9,29). The present study was performed to investigate the effect of 12 weeks of aerobic exercise training on the Th1/Th2 balance in asthmatic women. Our results showed that 12 weeks of moderate aerobic training significantly increased the Th1/Th2 ratio due to the reduction of IL-4 level in the serum ( Table 1).
Overproduction of IL-4 seems to contribute to the  Due to the significant reduction of cortisol and the insignificant increase in testosterone level, the testosteroneto-cortisol ratio (anabolic/catabolic ratio) did not change, which may suggest that our exercise training type and intensity (60-80% of MHR) were suitable for maintaining the homeostatic balance and health of asthmatic patients.
We found that the baseline cortisol and BMI had significant relationships with the Th1/Th2 ratio changes in the exercise group (

CONCLUSION
In conclusion, the results of the present study revealed that 12 weeks of aerobic exercise training cause a shift of the Th1/Th2 balance by cytokine changes and independent of sex hormones, cortisol, and BMI changes.